1. Field of the Invention
The present invention relates to image capture lenses and an image capture apparatus. More specifically, the present invention relates to a digital input apparatus (digital still camera, digital video camera, and the like) which takes in an image of a subject by means of a solid imaging device, and particularly to small-size image capture lenses suitable for a camera unit of a small-size electronic information apparatus, such as a mobile phone, PDA (Personal Digital Assistant, and the like) and an image capture apparatus using the image capture lenses.
2. Description of Related Art
In recent years, with wide-spreading of personal computers and the like, a digital still camera, a digital video camera, a camera module for mobile phones, and the like. (hereafter simply referred to as “digital camera”) which can take image information into a digital device easily, have been spreading to individual users. It is expected that such a digital camera continues to spread increasingly as an input apparatus for image information.
Further, the miniaturization of solid imaging devices, such as CCD (Charge Coupled Device), and, CMOS (Complementary Metal-Oxide Semiconductor), built in the digital camera, is progressing, and accordingly much more miniaturization is also required for the digital camera. For this reason, there is also a strong need for the miniaturization with respect to the image capture lens which occupies the largest volume in the digital input apparatus. Although, to reduce in size the solid imaging device is the easiest way of miniaturizing the image capture lens, it is necessary to reduce in size a light receiving element to this end. Further, the difficulty in manufacturing the solid imaging device increases, and performance required for the image capture lens also becomes high.
On the other hand, if the size of the solid imaging device is left as it is and the image capture lens is reduced in size, an exit pupil position approaches an image plane inevitably. If the exit pupil position approaches the image plane, an off-axis light flux emitted from the image capture lens may be obliquely incident on an image plane, and condensing performance of a micro lens provided in the front of the solid imaging device is not fully demonstrated. Thus, an issue arises in that brightness of the image is considerably different at the image center and the image edges. If the exit pupil position of the image capture lens is remotely located in order to solve this issue, it is no longer possible to avoid increase in size of the image capture lens as a whole.
Furthermore, due to the low-pricing competition in recent years, there is also a large demand for a reduction in cost with respect to the image capture lens.
As for the above demand, an image capture lens of a three-lens design is proposed in patent documents 1-3.